Abstract
An arbitrary pulse shape by compensating gain saturation in a solid-state Master oscillator power amplifier (MOPA) system made up of three Neodymium doped yttrium vanadate (Nd:YVO4) amplifiers is demonstrated. By investigating the amplifier dynamics in detail, car-shaped pulse shapes were obtained with compensated pulse distortion. Desired pulse shapes, such as multiple-step, square, parabolic, and Gaussian pulses, were achieved, with a high peak power level of 41.6 kW and a narrow linewidth less than 0.06 nm. In addition, through second harmonic generation (SHG), a green laser with different pulse shapes was obtained, with a maximum conversion efficiency of 42.6%.
Highlights
In the fields of optical sensing and Lidar applications, a long pulse duration, a good pulse shape, as well as a narrow spectral linewidth are required to achieve high precision measurements [1,2,3,4,5].Master oscillator power amplifier (MOPA) systems seeded by a modulated semiconductor diode is a cost-effective approach to obtaining the above parameters
To obtain green lasers with arbitrary pulse shapes, second harmonic generation was accomplished using the output of the above-mentioned MOPA system
Comparing the output power of the green laser with the same pulse energy but with different pulse shapes in Table 2, it was deduced that a smaller pulse duration, namely a higher peak power intensity, contributes to a higher conversion efficiency from a fundamental laser to the second harmonic wave
Summary
In the fields of optical sensing and Lidar applications, a long pulse duration, a good pulse shape, as well as a narrow spectral linewidth are required to achieve high precision measurements [1,2,3,4,5]. The inverse problem on how to obtain the desirable output waveform by actively controlling the input pulse shape and compensating the gain saturation effect should be solved. It is easy to obtain G(t) and control the pulse shape in fiber amplifiers, the peak power is limited by the nonlinear effect in the fiber [5,12], especially for the case of narrow spectral linewidth. In 2015, Lu Xu et al [16] demonstrated an experimental method of shaping the input pulse of a solid-state MOPA system by introducing a device made up of two polarizers, one Pockels cell and one half-wave plate. The MOPA laser, compared with the fiber laser, achieved a higher pulse energy and peak power by introducing more solid-state amplifiers, without the limit of a nonlinear effect. Based on the experimental results, how to generate desired pulse shapes through the SHG process is discussed
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